1. Field of the Invention
The present invention relates to a stable double covered elastomeric yarn, a process for making such a yarn, and fabric comprising such a yarn and, more especially, it relates to a yarn having a coordinated sheath twist orientation.
2. Discussion of the Background Art
Covered elastic yarns, such as single covered yarns obtained by winding an inelastic filament yarn or inelastic staple fiber around a core elastic yarn, and double covered yarns obtained by further winding around the single covered yarn a second inelastic filament yarn or inelastic staple fiber, are used in a variety of apparel applications. Such covered elastic yarns recently have come to be used in stretch woven applications that do not require a great deal of stretchability.
Japanese Published Patent Application No. 06-049736 (1994) discloses the use in elastic woven fabrics of an elastic polyurethane fiber covered with a multifilament yarn in which the weight ratio of the multifilament yarns to the elastic fiber is one to five. That is, the elastic fiber is 50% to about 80% of the weight of the covered yarn. However, the problems of fluff, stability, and hand that arise when the covering fiber is in staple form are not solved in this disclosure.
Further, typical stretch fabrics using conventional elastomeric polyurethane fibers have been deficient in that they have a low wet heat settability and tend to shrink on laundering. The covered yarn can also exhibit its instability in that the core yarn and sheath yarn can shift with respect to each other so that the elastic yarn slips in at cut edges of the fabric and the core yarn penetrates the covering yarn. Such yarns can also result in fluff formation and give fuzzy fabrics, or curl in the case of knit products. In order to enhance hot-wet stability, the heat-set temperature could be increased, but covered elastic yarns using thermally degradable fibers such as wool and acrylic staple as sheath yarns cannot tolerate wet temperatures of 100.degree. C. or higher in dyeing and finishing or dry temperatures of 160.degree. C. or higher because the soft hand can be lost and fabric strength reduced. A stable covered elastic yarn is still needed.